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NSCLCPhase 2NCT05773092

A Phase 2 Study of Osimertinib and S-1 in Treatment Resistant EGFR Mutant NSCLC

A Phase 2 study testing Oral S-1 + Oral Osimertinib in people with NSCLC, run by National Cancer Centre, Singapore at 1 site in Singapore.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
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Trial summary

The objective of this study is to determine best overall response rate (BOR) based on radiological assessment per RECIST v1.1 to combination of S-1 and Osimertinib in treatment-resistant EGFR mutant lung cancer. Read more about this study

Who is it for?
Ages 21 to 99 years
Conditions the study is for
NSCLC
What is being tested?
Oral S-1 + Oral Osimertinib
Type of treatment
Pill or oral medicine
Could I receive a placebo?
No, everyone receives an active treatment
How many people
30 participants
Where
1 siteSingapore
Study dates
1 Aug 2023to 31 Mar 2028
Phase
Phase 2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 21 to 99 years
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Patients must have histologically or cytologically confirmed EGFR mutant NSCLC.
  • Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) as >20 mm with conventional techniques or as >10 mm with spiral CT scan, MRI, or calipers by clinical exam.
  • Prior therapy: Patient with recurrent and/or metastatic EGFR mutant NSCLC, that has progressed on osimertinib as most recent line of treatment, and the primary doctor intends to continue with osimertinib treatment.
  • Patients with no matched alterations (tumor or plasma) where clinical trials or approved systemic anti-cancer therapy are available, are eligible
  • Patients with matched alterations on rebiopsy (tumor or plasma) who declined matching clinical trials, or approved systemic anti-cancer therapy, are eligible
  • Age ≥21 years.
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  • ECOG performance status ≤2 (Karnofsky ≥60%, see Appendix A).
  • Patients must have adequate organ and marrow function as defined below:
  • absolute neutrophil count ≥1,500/mcL
  • platelets ≥100,000/mcL
  • total bilirubin ≤ institutional upper limit of normal (ULN)
  • AST(SGOT)/ALT(SGPT) ≤3 × institutional ULN
  • creatinine ≤ institutional ULN OR glomerular filtration rate (GFR) ≥50 mL/min/1.73 m2
  • Human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial provided that DDI with osimertinib has been addressed.
  • For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated.
  • Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load.
  • Patients with treated brain metastases are eligible if follow-up brain imaging after central nervous system (CNS)-directed therapy shows no evidence of progression.
  • Patients with asymptomatic new or progressive brain metastases (active brain metastases) or leptomeningeal disease are eligible if the treating physician determines that immediate CNS specific treatment is not required and is unlikely to be required during the first cycle of therapy.
  • Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial.
  • Patients with known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, should have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification. To be eligible for this trial, patients should be class 2B or better.
  • The effects of S-1 on the developing human fetus are unknown. For this reason and because cytotoxic agents are known to be teratogenic, women of childbearing potential (WOCBP) must use appropriate method(s) of contraception. WOCBP must have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of HCG) within 24 hours prior to the start of treatment. Women must not be breastfeeding. Men who are sexually active with WOCBP must use any contraceptive method with a failure rate of less than 1% per year.
  • Ability to understand and the willingness to sign a written informed consent document.

Who cannot join

  • Patients who have had chemotherapy or radiotherapy within 4 weeks (6 weeks for nitrosoureas or mitomycin C) prior to entering the study or those who have not recovered from adverse events due to agents administered more than 4 weeks earlier (i.e., have residual toxicities > Grade 1) with the exception of alopecia.
  • Patients who are receiving any other investigational agents.
  • Patients are excluded if they have symptomatic brain metastases or leptomeningeal metastases.
  • History of allergic reactions attributed to compounds of similar chemical or biologic composition to S-1.
  • Concomitant medications: Patients should only be excluded from trial participation when clinically relevant known or predicted drug-drug interactions or potential overlapping toxicities will impact safety or efficacy. Please include scientific or clinically based rationale for exclusion.
  • Patients with uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations
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  • Pregnant women are excluded from this study because both compounds are potentially teratogenic.
  • Subjects with concomitant second malignancies (except adequately treated non-melanomatous skin cancers, in situ cervical cancers, localized prostate cancer or in situ breast cancer) are excluded unless a complete remission was achieved at least 3 years prior to study entry and no additional therapy is required or anticipated to be required
  • Prior organ allograft or allogeneic bone marrow transplantation
  • Prisoners or subjects who are involuntarily incarcerated
  • Subjects who are compulsorily detained for treatment of either a psychiatric or physical (eg, infectious disease) illness
  • Inability to comply with restrictions and prohibited activities/treatments in this study.

Trial locations and contacts

1 site in 1 country.

Singapore1 site

  • National Cancer Center Singapore

    Singapore, 169690

Other trials in Singapore

About this study

Official title: A Phase 2 Study of Osimertinib and S-1 in Treatment Resistant EGFR Mutant NSCLC (SOS-1 Study)

The objective of this study is to determine best overall response rate (BOR) based on radiological assessment per RECIST v1.1 to combination of S-1 and Osimertinib in treatment-resistant EGFR mutant lung cancer.

Read the detailed description

A lead-in phase of 6 patients will be initiated prior to the formal phase II study. The planned sample size is 27 patients (lead-in and phase II).

The primary objective of the study is to demonstrate that S-1 fixed dose 40 mg BD is safe and effective in EGFR metastatic lung cancer resistant to Osimertinib in terms of best overall response (BOR).

The secondary objective of this study will be to further analyse the Disease Control Rate at stipulated timepoints (6,12 and 24 months), Progression-free survival, Overall Survival, and also the Toxicity by CTCAE 5.0.

Conditions
NSCLC
Being tested
Oral S-1 + Oral Osimertinib
Keywords
EGFR mutant lung cancer, Progression on Osimertinib

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Oral S-1 + Oral OsimertinibDrug

    S-1 (40mg) will be given orally twice a day (daily) from Day 1 to 14 (21 day cycle), and Osimertinib (80mg) will be given orally daily continuously.

Study groups in NCT05773092
Study groupRoleWhat they receive
InterventionExperimentalOral S-1 + Oral Osimertinib
Receives: Drug: Oral S-1 + Oral Osimertinib

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Objective response rate (ORR)

    The efficacy of S-1 and Osimertinib. ORR is defined as the proportion of subjects who have best objective response (BOR) of CR or PR from start of combination treatment until disease progression or death due to any cause.

    Measured: Up to 2 years

Secondary outcomes (3)

  1. Disease control rate (DCR)

    DCR is defined as the proportion of subjects with a best response of CR, PR or SD.

    Measured: Up to 2 years

  2. Progression-free survival (PFS)

    PFS is defined as time from study entry until objective tumour progression, or death from any cause, whichever occurs first.

    Measured: Up to 3 years after end of treatment

  3. Overall survival (OS)

    OS is defined as time from study entry to death (from any cause).

    Measured: Up to 3 years after end of treatment

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted17 Mar 2023
  2. Study start1 Aug 2023
  3. Primary completion24 Oct 2025
  4. Study completion31 Mar 2028 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrolment
30 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT05773092
Sponsor's protocol ID
2022/2640
Status last verified
Jun 2026
First submitted
6 Mar 2023
Last updated
22 Jun 2026
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Oral S-1 + Oral Osimertinib in people with NSCLC, run by National Cancer Centre, Singapore at 1 site in Singapore.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 22 inclusion and 12 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 22 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Singapore. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Objective response rate (ORR) (time frame: Up to 2 years). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05773092.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 22 Jun 2026.

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